Field of Invention and Description of the Prior Art
This invention is a method and apparatus for automatically feeding discrete substrates into and out of a continuous vacuum chamber. In a preferred embodiment this device is used to feed discrete substrates one at a time into a continuously operating vacuum coating apparatus. The problem is to feed the substrates into the coating apparatus one at a time, without breaking the vacuum, contaminating the environment in the coating apparatus or allowing coating material to escape.
Batch processing has been used in the prior art; however, the obvious disadvantage has been low production and the need for highly trained labor to control the process. Continuous process apparatus has also been developed using baffles or flapper valves to allow workpieces to be fed singly into an open ended machine. The machine is continuously evacuated to maintain vacuum conditions in the interior while outside air constantly enters the machine through the baffles. This type of machine has been referred to as allowing air to enter the interior through "calibrated leaks" which are compensated for by continuous operation of the vacuum pumps.
In the present invention the vacuum chamber or associated coating apparatus may be held at vacuum under steady conditions without leakage or contamination by outside air. Additionally, the method and apparatus of this invention allows fully automatic and rapid feeding of workpieces into the vacuum chamber where the workpieces may be operated on in any manner.
This invention represents a specific improvement over the device patented by Robert L. Shrader in U. S. Pat. No. b 3,656,454 issued Apr. 18, 1972.